Shallow daily torpor, like hibernation, is an exaggerated form of mammalian sleep. Thus, understanding the neural mechanisms involved in regulation of either shallow torpor or deep hibernation will lend insight into the neural controls responsible for regulating normal euthermic mammalian sleep and wakefulness. Consequently, the ultimate goal of the proposed research plan is to understand the neural control of shallow daily torpor. The specific questions of interest are: 1) Which neural regulatory systems control the entrance into and arousal from torpor?, and, 2) How are other neural regulatory mechanisms influenced by the reduced body temperature which accompanies torpor? the research projects included in this proposal are designed to help answer question #1 and will specifically test the hypothesis that production of muscular atonia is an essential organizing event which leads to entrance into shallow torpor. The first sub-project will use decerebrate animals and electrical microstimulation to determine stereotaxic coordinates for pontine and medullary atonia centers. The second sub-project will use decerebrate animals and chemical micro- stimulation to document that the brainstem atonia centers are cholinoceptive. The third sub-project will use animals chronically implanted with microinjection cannulas aimed at the brainstem atonia centers and document production of muscular atonia following chemical microstimulation. The final project will use these same animals to determine if microinjection of pharmacological doses of carbachol into the atonia centers induces shallow torpor. In addition, this research proposal is designed to allow substantial student involvement. The student will be trained in basic techniques widely utilized in neurophysiological research. He/she will also learn basic experimental design, data reduction and statistical analysis, and manuscript and seminar preparation. These experiences will provide a sound base for and promote interest in more advanced training in biomedical research.